fix(vm): livemigration force handling for PreferForced/AlwaysForced

[danilrwx]

Description

Fixes live migration force handling in CLI and controller policy evaluation.

Why do we need it, and what problem does it solve?

d8 v evict and d8 v migrate always sent spec.force=false by default.
Because of that, PreferForced was effectively overridden to allowAutoConverge=false, so migrations were running without throttling even when policy expected forced convergence.

Also, for AlwaysForced we keep strict rejection only for explicit force=false, while force=nil follows policy defaults.

What is the expected result?

1. Set VM spec.liveMigrationPolicy: PreferForced.
2. Run d8 v evict <vm> (without --force).
3. Created VMOP should have spec.force unset (nil).
4. Migration configuration should keep allowAutoConverge=true.
5. For AlwaysForced:
   • force=nil -> valid
   • force=true -> valid
   • force=false -> rejected

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: vm
type: fix
summary: "CLI no longer sends force=false by default, and AlwaysForced policy now rejects only explicit force=false while preserving policy defaults for unset force."